Remove DashboardComponentDeleteSignalMixin from relevant views

[m4ra]

Check /var/log/django/django.log for the following deprecation warnings from any usage that is not expected.
"""Mixin which sends a project_component_updated or module_component_updated signal
when creating, updating or deleting an object via the HTTP POST method
(e.g. from the dashboard).
"""
If we have this warning, need to investigate further.